ABSTRACT
Recently focused-electron-beam-induced etching of silicon using molecular chlorine (Cl(2)-FEBIE) has been developed as a reliable and reproducible process capable of damage-free, maskless and resistless removal of silicon. As any electron-beam-induced processing is considered non-destructive and implantation-free due to the absence of ion bombardment this approach is also a potential method for removing focused-ion-beam (FIB)-inflicted crystal damage and ion implantation. We show that Cl(2)-FEBIE is capable of removing FIB-induced amorphization and gallium ion implantation after processing of surfaces with a focused ion beam. TEM analysis proves that the method Cl(2)-FEBIE is non-destructive and therefore retains crystallinity. It is shown that Cl(2)-FEBIE of amorphous silicon when compared to crystalline silicon can be up to 25 times faster, depending on the degree of amorphization. Also, using this method it has become possible for the first time to directly investigate damage caused by FIB exposure in a top-down view utilizing a localized chemical reaction, i.e. without the need for TEM sample preparation. We show that gallium fluences above 4 × 10(15) cm(-2) result in altered material resulting from FIB-induced processes down to a depth of â¼ 250 nm. With increasing gallium fluences, due to a significant gallium concentration close beneath the surface, removal of the topmost layer by Cl(2)-FEBIE becomes difficult, indicating that gallium serves as an etch stop for Cl(2)-FEBIE.
ABSTRACT
A new beam-assisted process for removing silicon from a surface in the nanometer scale in a conventional scanning electron microscope is presented. This approach is based on focused electron beam induced etching with pure chlorine gas being used as the precursor. In contrast to the established etching process using a focused ion beam (with or without the addition of a precursor), no amorphization and gallium implanting of the substrate takes place. The observed low etch rates facilitate removal with sub-nanometer precision. No spontaneous etching of silicon as in the case of xenon difluoride was observed. Etch rates of up to 4 nm min( - 1) could be achieved as well as a minimum feature size of below 80 nm. The effect of etching parameters like electron beam energy, electron beam accelerating voltage or pixel spacing were systematically examined. Finally, the underlying etching mechanism in terms of secondary electron interactions and precursor replenishment is discussed.